U.S. patent number 7,270,689 [Application Number 10/890,973] was granted by the patent office on 2007-09-18 for reformer.
This patent grant is currently assigned to K. E. M. Corporation, Toyo Engineering Corporation. Invention is credited to Hidetsugu Fujii, Yukuo Katayama, Katsuya Uehara, Fumitake Watanabe.
United States Patent |
7,270,689 |
Fujii , et al. |
September 18, 2007 |
Reformer
Abstract
A reformer for reacting a raw material gas to be reformed, with
an oxidizing agent gas and a reforming agent gas in the presence of
an oxidation catalyst and a reforming catalyst to obtain a
hydrogen-containing gas, including: a set of catalyst layers
consisting of an oxidation catalyst layer and a reforming catalyst
layer, and two or more inlets for feeding the oxidizing agent gas
to the oxidation catalyst and/or the reforming catalyst in plural
stages. The reformer can produce a hydrogen-containing gas without
forming a combustion region of a temperature of as high as one
thousand and several hundreds centigrade and can be manufactured at
a low cost.
Inventors: |
Fujii; Hidetsugu (Chiba,
JP), Watanabe; Fumitake (Chiba, JP),
Uehara; Katsuya (Chiba, JP), Katayama; Yukuo
(Tokyo, JP) |
Assignee: |
Toyo Engineering Corporation
(Tokyo, JP)
K. E. M. Corporation (Tokyo, JP)
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Family
ID: |
33475545 |
Appl.
No.: |
10/890,973 |
Filed: |
July 14, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050013752 A1 |
Jan 20, 2005 |
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Foreign Application Priority Data
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Jul 14, 2003 [JP] |
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2003-274179 |
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Current U.S.
Class: |
48/198.7;
422/198; 422/211; 422/222; 422/626; 48/127.9 |
Current CPC
Class: |
B01J
8/0453 (20130101); B01J 8/0492 (20130101); C01B
3/382 (20130101); B01J 2208/025 (20130101); B01J
2219/0277 (20130101); C01B 2203/00 (20130101); C01B
2203/0233 (20130101); C01B 2203/0844 (20130101); C01B
2203/1041 (20130101); C01B 2203/1052 (20130101); C01B
2203/1241 (20130101); C01B 2203/143 (20130101); C01B
2203/82 (20130101) |
Current International
Class: |
C01B
3/32 (20060101) |
Field of
Search: |
;48/127.9,198.7
;422/188-191,193-195,198,211,222 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 245 532 |
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Oct 2002 |
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EP |
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2000-319006 |
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Nov 2000 |
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JP |
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2003-112903 |
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Apr 2003 |
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JP |
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Primary Examiner: Ridley; Basia
Attorney, Agent or Firm: Knobbe Martens Olson & Bear,
LLP
Claims
What is claimed is:
1. A reformer for reacting a raw material gas to be reformed, with
an oxidizing agent gas and a reforming agent gas in the presence of
an oxidation catalyst and a reforming catalyst to obtain a
hydrogen-containing gas, comprising: a reactor vessel; a single set
of catalyst layers provided in the reactor vessel, said set of
catalyst layers consisting of one oxidation catalyst layer and one
first reforming catalyst layer provided downstream of the oxidation
catalyst layer; one second reforming catalyst layer provided
downstream of the first reforming catalyst layer, wherein the
oxidation catalyst layer, the first reforming catalyst layer, and
the second reforming catalyst layer are the only catalyst layers
provided in the reactor vessel; an inlet for feeding the oxidizing
agent gas to the oxidation catalyst layer, disposed inside the
oxidation catalyst layer; an inlet for feeding the oxidizing agent
gas between the first reforming catalyst layer and the second
reforming catalyst layer; and an inlet for feeding the raw material
gas into the reactor vessel, disposed inside the oxidation catalyst
layer close to the inlet for feeding the oxidizing agent gas
disposed inside the oxidation catalyst layer, wherein each of the
inlets for feeding the oxidizing agent gas and the inlet for
feeding the raw material gas are separately coupled to the reactor
vessel with regard to gas mixing.
2. The reformer according to claim 1, wherein at least one of the
inlets for feeding the oxidizing agent gas has a multi-nozzle
structure.
3. The reformer according to claim 1, wherein the reforming
catalyst is a nickel-based catalyst.
4. The reformer according to claim 1, wherein the inlet for feeding
the oxidizing agent gas disposed inside the oxidation catalyst
layer and the inlet for feeding the raw material gas disposed
inside the oxidation catalyst layer are constructed by a
double-pipe structure having an end inside the oxidation catalyst
layer.
5. A reformer for reforming a raw material gas to obtain a
hydrogen-containing gas therefrom, comprising: a reactor vessel
having (i) an inlet end from which a raw material gas, a reforming
agent gas, and an oxidizing gas are introduced into the reactor
vessel, wherein piping for feeding the raw material gas and piping
for feeding the oxidizing gas are separately coupled to the inlet
end with respect to gas mixing, (ii) an outlet end from which a
hydrogen-containing gas is discharged from the reaction vessel, and
(iii) a side inlet from which an oxidizing gas is introduced into
the reaction vessel; one oxidation catalyst layer provided in the
reaction vessel for receiving the raw material gas, the reforming
gas, and the oxidizing gas from the inlet end and oxidizing the raw
material gas, wherein the piping for feeding the raw material gas
and the piping for feeding the oxidizing gas of the inlet end
extend inside the most upstream oxidation catalyst layer and are
open therein; one first reforming catalyst layer provided
downstream of the oxidation catalyst layer, for reforming the
oxidized gases passing therethrough; and one second reforming
catalyst layer provided downstream of the first reforming catalyst
layer to produce a hydrogen-containing gas which is discharged from
the reaction vessel through the outlet end, wherein the side inlet
is positioned between the first reforming catalyst layer and the
second reforming catalyst layer to supply an oxidizing gas to the
reforming catalyst layer, wherein the oxidation catalyst layer, the
first reforming catalyst layer, and the second reforming catalyst
layer are the only catalyst layers provided in the reaction
vessel.
6. The reformer according to claim 5, wherein the inlet end
comprises an inlet nozzle for introducing the raw material gas and
the reforming agent gas, and a gas feeding pipe for the oxidation
gas.
7. The reformer according to claim 6, further comprising a steam
line connected to the inlet nozzle.
8. The reformer according to claim 6, wherein the gas feeding pipe
has a branch pipe connected to the side inlet.
9. The reformer according to claim 5, wherein the oxidation
catalyst is a palladium-containing catalyst, a manganese-containing
catalyst, a lanthanum-containing catalyst, a vanadium-containing
catalyst, or a barium-containing catalyst.
10. The reformer according to claim 5, wherein the reforming
catalyst is a Ni-containing catalyst.
11. The reformer according to claim 5, wherein the inlet end is
provided with a multi-nozzle structure for introducing the
oxidizing agent gas therethrough.
12. The reformer according to claim 5, wherein the side inlet has a
multi-nozzle structure.
13. The reformer according to claim 5, wherein the piping for
feeding the oxidizing agent gas disposed inside the oxidation
catalyst layer and the piping for feeding the raw material gas
disposed inside the oxidation catalyst layer are constructed by a
double-pipe structure having an end inside the oxidation catalyst
layer.
14. A method for reforming a raw material gas to obtain a
hydrogen-containing gas therefrom, comprising: introducing a
hydrocarbon-containing raw material gas, a reforming agent gas, and
an oxidizing gas into a reactor vessel, wherein the raw material
gas and the oxidizing gas are separately introduced inside an
oxidation catalyst layer in the reaction vessel without gas mixing;
passing the hydrocarbon-containing raw material gas, the reforming
agent gas, and the oxidizing gas through the oxidation catalyst
layer; and passing gases discharged from the oxidation catalyst
layer having a temperature of 800.degree. C.-1,200.degree. C.
through a first reforming catalyst layer to reform the oxidized
gases; passing gases discharged from the first reforming catalyst
layer through a second reforming catalyst layer while separately
supplying an additional oxidizing gas between the first reforming
catalyst layer and the second reforming catalyst layer, thereby
producing a hydrogen-containing gas.
15. The method according to claim 14, wherein the raw material gas
is selected from the group consisting of methane, ethane, propane,
butane, natural gas, methanol, dimethyl ether, and partially
reformed gasses of the foregoing.
16. The method according to claim 14, wherein the reforming agent
gas is a gas which endothermically reacts with the raw material
gas.
17. The method according to claim 16, wherein the reforming agent
gas is steam or carbon dioxide gas.
18. The method according to claim 14, wherein the oxidizing gas is
oxygen, oxygen-enriched air, or air.
19. The method according to claim 14, wherein the
hydrogen-containing gas is a gas containing hydrogen as a major
component and further containing carbon monoxide, carbon dioxide, a
hydrocarbon, and/or steam.
20. The method according to claim 14, wherein the
hydrogen-containing gas is a gas containing carbon monoxide as a
major component and further containing hydrogen, carbon dioxide, a
hydrocarbon, and/or steam.
21. The method according to claim 14, wherein the oxidation
catalyst is a palladium-containing catalyst, a manganese-containing
catalyst, a lanthanum-containing catalyst, a vanadium-containing
catalyst, or a barium-containing catalyst.
22. The method according to claim 14, wherein the reforming
catalyst is a Ni-containing catalyst.
23. The method according to claim 14, wherein the oxidizing gas
supplied to the oxidation catalyst layer and the additional
oxidizing gas are the same gas.
24. The method according to claim 14, wherein the gases entering
the oxidation catalyst layer has a temperature of 300.degree.
C.-600.degree. C.
25. The method according to claim 14, wherein the raw material gas
is separately introduced inside the oxidation catalyst layer.
26. The method according to claim 14, wherein the oxidizing gas is
introduced into the reactor vessel through an inlet having a
multi-nozzle structure.
27. The method according to claim 14, wherein the additional
oxidizing gas is introduced into the reactor vessel through an
inlet having a multi-nozzle structure.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reformer for obtaining a
hydrogen-containing gas from a raw material gas such as a natural
gas. Particularly, the present invention relates to a reformer for
obtaining a hydrogen-containing gas by reacting a raw material gas
to be reformed, with an oxidizing agent gas and a reforming agent
gas. The hydrogen-containing gas thus obtained may be utilized, for
example, as a fuel for a fuel cell or as a synthetic gas which is a
raw material for synthesis of methanol, ammonia, hydrocarbon oil or
hydrocarbons.
2. Discussion of the Background
As a process for producing a hydrogen-containing gas, there are
well known a steam reforming process in which steam is used as a
reforming agent for reforming a raw hydrocarbon material such as a
natural gas, and a partial oxidation process in which a raw
hydrocarbon material, such as a natural gas, and an oxidizing
agent, such as oxygen, oxygen-enriched air and air, are used.
Referring to FIG. 2, there is explained a process for producing a
hydrogen-containing gas using a steam reformer of internal heating
type, wherein a raw material natural gas is reacted with an
oxidizing agent gas and a reforming agent gas to obtain a
hydrogen-containing gas.
Reactor 111 is constituted by combustion zone 121 equipped with
burner 112, which is provided at the upper portion of the reactor,
and reforming zone 122 filled with a steam reforming catalyst,
which is provided at the lower portion of the reactor. The inside
of reactor 111 is lined with refractory 113 such as brick for
resistance to a high-temperature flame. Mixed gas 101 of a natural
gas and a reforming agent gas is mixed with oxidizing agent 102
such as air at burner 112, and part of the natural gas is partially
combusted. The heat generated by this combustion gives rise to a
steam reforming reaction between the hydrocarbons in the remaining
natural gas and the reforming agent gas during their passage
through reforming zone 122; thereby, hydrogen-containing gas 103
composed mainly of hydrogen and carbon monoxide is produced.
In the above partial combustion, a flame is formed. When the flame
contacts with the catalyst of reforming zone 122 at the lower
portion of the reactor, a temperature of as high as one thousand
and several hundreds centigrade is reached and the catalyst is
melt; as a result, phenomena such as decrease in catalyst activity
appear. Therefore, various proposals have been made to avoid such
problems.
For solving the above problems, JP-A-2000-319006 discloses a
technique for making uniform the temperature of the catalyst layer.
This document discloses a fuel reforming apparatus for forming a
hydrogen-containing gas, wherein a gaseous mixture of a fuel gas,
steam and an oxygen-containing gas is introduced into a reactor
having a catalyst filled in its upstream side and another catalyst
filled in its downstream side to form a hydrogen-containing
gas.
In this apparatus, there is provided, in a part of the catalyst
layer at the upstream side of the reactor, non-contact passages in
which the gas introduced makes no contact with the catalyst. In
this structure, the gaseous mixture of a fuel gas, steam and an
oxygen-containing gas, fed into the catalyst layer at the upstream
side of the reactor forms a high-temperature zone; meanwhile, the
gaseous mixture passing through the non-contact passages makes no
direct contact with the high-temperature zone, but contacts the
high-temperature zone via the walls of the non-contact passages and
reaches the catalyst layer at the downstream side of the
reactor.
As a result, the gas passing through the non-contact passages is
exposed to a high temperature. Since this gaseous mixture contains
oxygen, it is highly possible that the gaseous mixture forms a
detonating gas depending upon the case.
Further, JP-A-2003-112903 discloses a small-sized fuel reformer in
which the heat generated in a combustion catalyst part is
transferred efficiently to a stream reforming catalyst part and
thereby the generation of a reformed gas at the stream reforming
part is enhanced.
In the above fuel reformer, the interface between the combustion
catalyst part and the steam reforming catalyst part is formed in
such a conical shape that the axial direction dimension (height) of
the vertical cross section of the steam reforming catalyst part is
made gradually smaller as the position of the height shifts from
the periphery of the vertical cross section to its center; the
reaction heat generated in the combustion catalyst part can be
transferred to the steam reforming catalyst part more efficiently;
and the formation of reformed gas is enhanced.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a reformer which
can produce a hydrogen-containing gas without generating a
combustion zone of temperature of as high as one thousand and
several hundreds centigrade, and which can be manufactured at lower
cost.
The inventors found that the inner temperature of a reformer which
was packed with an oxidation catalyst and a reforming catalyst can
be kept low by introducing a raw material to be reformed, an
oxidizing agent gas and a reforming agent gas into the reformer and
feeding the oxidizing agent gas in plural stages to the reformer.
The present invention has been achieved based on this finding.
The present invention provides a reformer for reacting a raw
material gas to be reformed, with an oxidizing agent gas and a
reforming agent gas in the presence of an oxidation catalyst and a
reforming catalyst to obtain a hydrogen-containing gas,
comprising:
a set of catalyst layers consisting of an oxidation catalyst layer
and a reforming catalyst layer, and
two or more inlets for feeding the oxidizing agent gas to the
oxidation catalyst and/or the reforming catalyst in plural
stages.
In the reformer of the present invention, a second reforming
catalyst layer may be further provided, and the inlets may be
arranged at a location where the oxidation agent gas is able to be
fed to said set of catalyst layers and at a location where the
oxidation agent gas is able to be fed to the second reforming
catalyst layer.
In the reformer of the present invention, the inlets may be
arranged at different locations where the oxidation agent gas is
able to be fed to said set of catalyst layers.
In the reformer of the present invention, two or more of the sets
of catalyst layers may be provided, and the inlets may be arranged
at locations where the oxidation agent gas is able to be fed to
each set of catalyst layers.
By using the oxidation catalyst, it is possible to lower the
reaction start temperature of the reformer; by feeding the
oxidizing agent gas in plural stages, it is possible to make the
temperature distribution inside the reformer more uniform and to
lower the level of the temperature distribution; as a result, it is
possible to eliminate expensive refractory such as brick and to
reduce manufacturing costs of a reformer. Further, the low
temperature inside the reformer can suppress the deterioration of
the catalysts and coke formation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic drawing showing an embodiment of the reformer
of the present invention.
FIG. 2 is a schematic drawing showing a conventional reformer.
FIG. 3 is a drawing showing modes of the gas-feeding method
employed in the present invention.
FIG. 4 is a schematic drawing showing another embodiment of the
reformer of the present invention.
FIG. 5 is a graph showing the catalyst layer temperature
distribution seen in Example 1.
FIG. 6 is a graph showing the catalyst layer temperature
distribution seen in Example 2.
FIG. 7 is a graph showing the catalyst layer temperature
distribution seen in Comparative Example 1.
FIGS. 8 and 9 are schematic drawings showing other embodiments of
the reformer of the present invention.
FIG. 10 illustrates an example of an inlet for feeding the
oxidizing agent gas, (a) is a top view, (b) is a side view.
1: raw material to be reformed (raw material gas), 2: reforming
agent gas, 2a: steam, 2b: carbon dioxide, 3: oxidizing agent gas,
4: mixed raw material gas (gaseous mixture of raw material gas and
reforming agent gas), 5: hydrogen-containing gas, 11: reactor
vessel, 12: oxidation catalyst layer, 13, 15: reforming catalyst
layer, 14: set of catalyst layers, 21, 22: line, 31: pipe for
feeding raw material gas, 32: oxidizing agent gas feeding pipe, 33:
second oxidizing agent gas feeding pipe, 34: third oxidizing agent
gas feeding pipe, 41: inlet nozzle, 42: outlet nozzle, 51: header,
52: nozzle, 53: oxidizing agent gas feeding pipe, 101: gaseous
mixture of natural gas and reforming gas, 102: oxidizing agent,
103: hydrogen-containing gas, 111: reactor, 112: burner, 113:
refractory, 121: combustion zone, 122: reforming zone.
DETAILED DESCRIPTION OF THE INVENTION
By using an oxidation catalyst, which is also referred to as a
combustion catalyst, it is unnecessary to generate, with a burner
or the like, a combustion zone of high temperature of as high as
one thousand and several hundreds centigrade in order to give rise
to combustion, oxidation can be started at a temperature of several
hundreds centigrade, accordingly a hydrogen-containing gas can be
produced at a low cost.
As the raw material gas to be reformed, there may be used a known
raw material which can be reformed to produce a hydrogen-containing
gas, or a gas obtained by vaporizing thereof if necessary. As a
preferred example, there can be mentioned a gas containing at least
one selected from the group consisting of methane, ethane, propane,
butane, natural gas, methanol, dimehtyl ether and partially
reformed gases thereof.
The above raw material gas may include hydrogen and/or carbon
dioxide added from outside.
The reforming agent gas endothermically reacts with the raw
material gas to produce a hydrogen-containing gas. As the reforming
agent gas, there can be mentioned a gas containing at least one
selected from the group consisting of steam and carbon dioxide gas.
The reforming agent gas may be steam, carbon dioxide or a mixed gas
of steam and carbon dioxide.
The oxidation agent gas oxidizes the raw material gas. Since the
oxidation reaction is exothermic, the oxidation agent gas may be
used for raising the temperature inside the reactor. Also, the
oxidizing agent gas may partially oxidize the raw material to
produce a hydrogen-containing gas. As a preferred example of the
oxidizing agent gas, there can be mentioned oxygen, oxygen-enriched
air, or air.
As the hydrogen-containing gas, there can be mentioned a gas
containing hydrogen as a major component and also containing carbon
monoxide, carbon dioxide, a hydrocarbon such as methane, steam,
etc., and a gas containing carbon monoxide as a major component and
also containing hydrogen, carbon dioxide, a hydrocarbon such as
methane, steam, etc.
An embodiment of the present invention is described in detail
referring to FIG. 1.
A reactor vessel 11 is equipped with an inlet nozzle 41; a set 14
of catalyst layers consisting of an oxidation catalyst layer 12
packed with an oxidation catalyst and a reforming catalyst layer 13
packed with a reforming catalyst; a second oxidizing agent
gas-feeding pipe 33; a reforming catalyst layer 15 packed with a
reforming catalyst; and an outlet nozzle 42.
The inlet nozzle 41 includes a raw material gas-feeding pipe 31 and
an oxidizing agent gas-feeding pipe 32.
A raw material gas 1 (e.g. a natural gas) to be reformed and a
reforming agent gas 2 are mixed to become a mixed raw material gas
4, pass through line 21, and are fed to the raw material
gas-feeding pipe 31 provided at the inlet portion of the reactor
vessel 11. An oxidizing agent gas 3 passes through line 22, is fed
to the oxidizing agent gas-feeding pipe 32, and is mixed with the
mixed raw material gas 4 at the inlet nozzle 41 provided upstream
of the set 14 of catalyst layers.
Here, the reforming agent gas 2 is mixed with the raw material gas
1 before entering the reactor vessel. However, the reforming agent
gas 2 need not be mixed with the raw material gas 1 and may be
mixed with the oxidizing agent gas 3 instead before entering the
reactor vessel. The reforming agent gas 2 may be mixed as necessary
with either or both of the oxidizing agent gas 3 and the raw
material gas 1. The reforming agent gas need not be mixed
beforehand, and each of the reforming agent gas, the raw material
gas and the oxidizing agent gas may be fed independently to the
reactor vessel.
In the embodiment shown in FIG. 1, the raw material gas-feeding
pipe 31 and the oxidizing agent gas-feeding pipe 32 are integrated
to make the inlet nozzle 41. However, the two pipes need not be
integrated and a plurality of pipes may be individually used as
necessary in order to feed each gas. There is no particular
restriction as to the constitution of inlet nozzle 41. It is
preferable to consider uniformity of feeding of gases to the
oxidation catalyst layer 12, in arranging the raw material
gas-feeding pipe 31 and the oxidizing agent gas-feeding pipe
32.
The openings of inlet nozzle 41 are provided, in FIG. 1, above the
oxidation catalyst layer 12 but may be provided at the uppermost
part (inside) of the oxidation catalyst layer 12.
In FIG. 3 are shown examples of the state in which the openings of
inlet nozzle 41 are provided. FIG. 3(a) illustrates a case in which
the feeding pipes and the catalyst layer are apart, and FIG. 3(b)
illustrates another case in which the openings of feeding pipes are
provided at the uppermost part of the catalyst layer.
In FIGS. 3(a) and 3(b), a solid (black) arrow indicates a flow of
the raw material gas fed from the raw material gas-feeding pipe 31
to the combustion catalyst layer 12, and outlined (white) arrows
indicate a flow of the oxidizing agent gas fed from the oxidizing
agent gas-feeding pipe 32 to the combustion catalyst layer 12.
In FIG. 1 is shown a set 14 of catalyst layers provided inside
reactor vessel 11, in which the oxidation catalyst layer 12 and the
reforming catalyst layer 13 are formed consecutively.
The mixed raw material gas 4 and a part of the oxidizing agent gas
3 are fed to the catalyst layer 12 packed with the oxidation
catalyst, via the inlet nozzle 41, at a temperature at which the
oxidation catalyst functions.
A preferred temperature at which gases are fed to the oxidation
catalyst layer, depends upon the compositions of the gases. A
relatively low temperature is preferred when hydrogen, which has
quick oxidation rate, is contained in a large amount. A relatively
high temperature is preferred when hydrocarbon components such as
methane and the like are contained in a large amount.
The mixed raw material gas and the oxidizing agent gas are reacted
with each other on the oxidation catalyst to form oxidation
products. The oxidation products are carbon monoxide, carbon
dioxide, water, etc. and a large amount of heat is generated by the
reaction.
As the combustion catalyst, there may be used an ordinary
commercially available catalyst such as palladium based, manganese
based, lanthanum based, vanadium based or barium based catalyst.
The shape thereof is, for example, a pellet, a ring or a spoke. The
combustion catalyst may be formed by extrusion molding.
The oxidation reaction is started preferably at a condition that
the feeding gas temperature is at least 300.degree. C. and at most
600.degree. C., and is ended preferably at 800.degree. C. or more
and 1,200.degree. C. or less. The combustion products are then fed
consecutively from oxidation catalyst layer 12 to reforming
catalyst layer 13. It is preferable to keep the temperature of
oxidation reaction at most 1,200.degree. C. from a viewpoint of
suppressing carbon deposition from the carbon-containing components
included in the raw material gas 1.
The ending temperature of the combustion in the oxidation catalyst
layer 12 depends upon the properties and feed amounts of the mixed
raw material gas and the oxidizing agent gas. Therefore, the
oxidation catalyst layer is preferably designed, for example, in
plural stages as necessary in consideration of the maximum
temperature of oxidation catalyst layer 12. For example, two sets
14a and 14b of catalyst layers may be consecutively provided inside
the reactor vessel 11 as shown in FIG. 8. Here, the set 14a has
oxidation catalyst layer 12a and reforming catalyst layer 13a, and
the set 14b has oxidation catalyst layer 12b and reforming catalyst
layer 13b.
The combustion gas, having a temperature of 800.degree. C. to
1,200.degree. C. for example, after the combustion is fed
consecutively to the reforming catalyst layer 13. In the reforming
catalyst layer 13, a hydrogen-containing gas is formed by steam
reforming reaction. The steam reforming reaction is as a whole an
endothermic reaction requiring a large amount of heat.
In the mode shown in FIG. 1, an exothermic reaction generating a
large amount of heat takes place in the oxidation catalyst layer
12; successively, an endothermic reaction takes place in the
reforming catalyst layer 13 and the heat generated in the oxidation
catalyst layer 12 is used effectively.
As the reforming catalyst, there may be used a commercially
available catalyst for steam reforming such as Ni based catalyst.
As the reforming catalyst, there are preferably used, for example,
catalysts described in JP-A-2-043952 (1990), JP-A-4-059048 (1992),
JP-A-9-299798 (1997), etc.
In this mode, another reforming catalyst layer 15 is formed
downstream of the reforming catalyst layer 13. In the reforming
catalyst layer 15, the steam reforming reaction proceeds further.
By feeding oxidation agent gas between the layers 13 and 15, it is
possible to give rise to combustion reaction. Here, unreacted raw
material, hydrogen and/or carbon monoxide may be combustible
because the gas temperature in this region is high enough. If
necessary, another combustion catalyst layer may be provided above
the reforming catalyst layer (in this case, as shown in FIG. 4,
another set 14b may be provided instead of the reforming catalyst
layer 15) in order to enhance the combustion reaction. The
combustion raise the temperature of the gas which enters reforming
catalyst layer 15 (or 13b in the embodiment shown in FIG. 4) which
is the most downstream catalyst layer, and therefore, concentration
of unreacted raw material gas in product gas 5 may be lowered. For
example, in case that the raw material gas is methane, it is
preferable to keep the temperature of the lower end of the
reforming catalyst layer 15 (or 13b in the embodiment shown in FIG.
4) at least 900.degree. C. and at most 1000.degree. C. in order to
remarkably reduce methane content in product gas 5. For this
purpose, oxidation agent gas may be fed to the layer 15 as
described above.
The hydrogen-containing gas after the completion of the steam
reforming reaction passes through the outlet nozzle 42 and is
obtained as a hydrogen-containing gas product via line 5.
It is known to utilize carbon dioxide which is fed from outside or
recycled in order to increase the efficiency of steam reforming
reaction. In this case, the ratio of feed amounts of steam, carbon
dioxide, etc. may be determined based on the charts shown on page
71 of "Hydrocarbon Processing" January, 1986.
The oxidizing agent gas may be fed in plural stages to the
oxidation catalyst when the maximum temperature of the oxidation
catalyst layer 12 is high depending upon the properties of the raw
material, etc. or when the maximum temperature is desired to be
made as low as possible. For example, two sets 14a and 14b of
catalyst layers may be provided in reactor vessel 11, and oxidizing
agent gas may be fed to each set of the catalyst layers via
oxidizing agent gas feeding pipe 32 and second oxidizing agent gas
feeding pipe 33 respectively as shown in FIG. 9. The embodiment
shown in FIG. 9 has reforming catalyst layer 15 downstream of the
two sets 14a and 14b, and oxidizing agent gas is fed to the
reforming catalyst layer 15 via third oxidizing agent gas feeding
pipe 34.
As the number of the stages for feeding the oxidizing agent gas are
more, the maximum temperature of the oxidation catalyst layer 12 is
lower; however, the reformer becomes more complex and the advantage
in economical efficiency, which is caused by lowering the maximum
temperature, may be reduced. Meanwhile, as the number of the stages
for feeding the oxidizing agent gas are less, the temperature of
the oxidation catalyst layer 12 is higher and the structure of the
reformer becomes simpler; however, a higher quality material may be
needed for the structure depending upon the case and the reformer
may possibly become more expensive. Thus, it is preferred to design
the reformer in consideration of these factors.
In FIG. 1, a part of oxidizing agent gas 3 is fed into the inlet
nozzle 41 and the remainder is fed into the second oxidizing agent
gas-feeding pipe 33 which is provided between the reforming
catalyst layer 13 and the reforming catalyst layer 15. In this
case, the reformer has two inlets for feeding the oxidizing agent
gas to the oxidation catalyst and/or the reforming catalyst in
plural stages. Among the two inlets, one is the opening of the
oxidizing agent gas-feeding pipe 32, and through this inlet, the
oxidizing agent gas is fed to the oxidation catalyst layer 12. The
other inlet is the opening of the second oxidizing agent
gas-feeding pipe 33, and through this inlet, the oxidizing agent
gas is fed to the reforming catalyst layer 15.
Alternatively, when no reforming catalyst layer 15 is provided, an
appropriate amount of the oxidizing agent gas may be fed into the
reforming catalyst layer 13 besides the oxidizing agent gas fed
through the inlet nozzle 41. A reformer of this case, which is not
shown in figures, may have the same structure as the reformer
illustrated in FIG. 1, except that the second oxidizing agent
gas-feeding pipe is connected to the reforming catalyst layer 13.
Also in this case, the reformer has two inlets for feeding the
oxidizing agent gas to the oxidation catalyst and/or the reforming
catalyst in plural stages. One is the opening of the oxidizing
agent gas-feeding pipe 32, and through this inlet, the oxidizing
agent gas is fed to the oxidation catalyst layer 12. The other
inlet is an opening of the second oxidizing agent gas-feeding pipe
which opens into the reforming catalyst layer 13.
There are provided gaps between catalyst layers 13 and 15 in FIG.
1, between layers 13a and 12b in FIG. 4, between layers 13b and 15
in FIG. 8, and between layers 13a and 12b and between layers 13b
and 15 in FIG. 9. Such gap may be provided or may not be
provided.
The inlet for feeding the oxidizing agent gas may have multi-nozzle
structure. For example, as shown in FIG. 10, two or more nozzles 52
and oxidizing agent gas feeding pipe 53 are connected to header 51
which may form a circular shape. This structure is effective in
feeding the oxidizing agent gas more uniformly into the catalyst
layer, and particularly preferable when the above-described gap is
not provided.
EXAMPLES
The present invention is described in detail below by way of
non-limiting examples.
Example 1
Using a reformer shown in FIG. 1, a hydrogen-containing gas was
obtained using methane gas as raw material gas 1 to be reformed,
steam as reforming agent gas 2, and oxygen as oxidizing agent gas
3. As shown in FIG. 1, mixed raw material gas 4 and a part of
oxidizing agent gas 3 were fed into a space above oxidation
catalyst layer 12 and the remainder of oxidizing agent gas 3 was
fed into second oxidizing agent gas-feeding pipe 33. The amount of
the oxidizing agent gas fed above the oxidation catalyst layer was
36% and the amount of the oxidizing agent gas fed into the second
oxidizing agent gas-feeding pipe was 64% based on the total
oxidizing agent gas fed.
Mixed raw material gas 4 and the oxidizing agent gas were fed into
reactor vessel 11 at 450.degree. C. There was a gradual temperature
increase in the catalyst layers inside the reformer from the start
of gas feeding.
The reactor vessel used had an internal diameter of 35 mm and was
made of a heat resistant alloy (trade name: KHR 35 CT, manufactured
by Kubota corporation).
A set 14 of catalyst layers was 40 mm in height of packed oxidation
catalyst and 20 mm in height of packed reforming catalyst.
As the oxidation catalyst, a supported Mn based oxidation catalyst
was used.
Reforming catalyst layer 15 provided downstream of the set 14 had a
packed height of 300 mm and was filled with a Ni based
catalyst.
The pressure was 0.68 MPa, S/C ratio was 2.3, SV.sub.0 (oxidation
catalyst) was 140,000/hour, and SV.sub.0 (reforming catalyst) was
9,000/hour.
Here, the S/C ratio is a ratio of moles of steam (S) to moles of
carbon (C) in the raw material gas. SV.sub.0 (oxidation catalyst)
and SV.sub.0 (reforming catalyst) are space velocities at 0.101 Mpa
and 0.degree. C. in the oxidation catalyst layer and the reforming
catalyst layer respectively.
Under the above conditions, the maximum temperature in all the
catalyst layers inside the reactor vessel was 1,100.degree. C. The
temperature distribution in all the catalyst layers inside the
reactor vessel is shown in FIG. 5 and the result of temperature
measurement is shown in Table 1. In FIG. 5, the abscissa is a
normalized value of the distance from the upper end of the set 14
of catalyst layers, and the upper end of the set 14 was taken as 0
(zero) and the lower end of reforming catalyst layer 15 was taken
as 1.
Example 2
A reformer shown in FIG. 4 having two sets of catalyst layers, 14a
and 14b, was used. The set 14a has oxidation catalyst layer 12a and
reforming catalyst layer 13a, and the set 14b has oxidation
catalyst layer 12b and reforming catalyst layer 13b.
There were used methane gas as raw material gas 1 to be reformed,
and steam 2a and carbon dioxide 2b as reforming agent gases. Using
their mixture as mixed raw material gas 4 and oxygen as oxidizing
agent gas 3, a synthetic gas was produced. The mixed raw material
gas 4 and a part of oxidizing agent gas 3 were fed into a space
above combustion catalyst layer 12a, as shown in FIG. 4. 50% of the
total feed amount of the oxidizing agent gas was fed into the inlet
portion of the reactor vessel 11 via oxidizing agent gas feeding
pipe 32, and the remaining 50% was fed into the intermediate
portion, which is a space between the sets 14a and 14b, via second
oxidizing agent gas feeding pipe 33. In this case, the reformer has
two inlets for feeding the oxidizing agent gas to the oxidation
catalyst and/or the reforming catalyst in plural stages. Among the
two inlets, one is the opening of the oxidizing agent gas-feeding
pipe 32, and through this inlet, the oxidizing agent gas is fed to
the oxidation catalyst layer 12a. The other inlet is the opening of
the second oxidizing agent gas-feeding pipe 33, and through this
inlet the oxidizing agent gas is fed to the oxidation catalyst
layer 12b.
The mixed raw material gas and 50% of oxidizing agent gas 3 were
fed into the reactor vessel at 450.degree. C. via inlet nozzle 41.
There was a gradual temperature increase from the start of gas
feeding. Incidentally, the remaining 50% of oxidizing agent gas 3
is fed into the reactor vessel at 450.degree. C. via second
oxidizing agent gas-feeding pipe 33.
The reactor vessel used had an internal diameter of 35 mm and was
made of a heat resistant alloy (trade name: KHR 35 CT, manufactured
by Kubota corporation).
Each of the two sets 14a and 14b was 40 mm in height of packed
oxidation catalyst and 160 mm in height of packed reforming
catalyst.
As the oxidation catalyst, a supported Mn based catalyst was
used.
As the reforming catalyst, a Ni based catalyst was used.
The pressure was 0.68 MPa, S/C ratio was 2.3, CO.sub.2/CH.sub.4 was
0.004, and O.sub.2/CH.sub.4 was 0.66.
Here, the CO.sub.2/CH.sub.4 is a molar ratio of carbon dioxide
(CO.sub.2) to methane (CH.sub.4), and the O.sub.2/CH.sub.4 is a
molar ratio of oxygen (O.sub.2) to methane (CH.sub.4).
Under the above conditions, the maximum temperature in the reactor
vessel was 1,050.degree. C. The temperature distributions of the
catalyst layers inside the reactor vessel are shown in FIG. 6 and
the result of temperature measurement is shown in Table 1. In FIG.
6, the abscissa is a normalized value of the distance from the
upper end of upstream the set of catalyst layers 14a, and the upper
end of the set 14a was taken as 0 (zero) and the lower end of the
set of catalyst layers 14b was taken as 1.
Comparative Example 1
Using methane gas as a raw material gas to be reformed and a mixed
gas of oxygen and steam as an oxidizing agent gas, a synthetic gas
was obtained using a reformer having a structure shown in FIG. 2.
Feeding of the gases to the reformer was made at 600.degree. C. The
temperature distribution of catalyst layer in the reactor vessel is
shown in FIG. 7 and the gas conditions and result of temperature
measurement are shown in Table 1. In FIG. 7, the abscissa is a
normalized value of the distance from the upper end of reforming
zone 122, and the upper end of reforming zone 122 was taken as 0
(zero) and the lower end of reforming zone 122 was taken as 1.
TABLE-US-00001 TABLE 1 Example Example Comparative 1 2 Example 1
Temperature of gas feeding (.degree. C.) Raw material gas 450 450
600 Oxidizing agent gas 450 450 600 Maximum temperature inside
1,100 1,050 2,500 reactor vessel (.degree. C.) Maximum temperature
of -- -- 1,600 reforming zone(122) (.degree. C.)
* * * * *